Assuming you're referring to watching videos on the Internet, it's usually caused by a lack of bandwidth. That lack of bandwidth can be caused by your local network, your ISP or the service you're using (e.g. YouTube).
Assuming you're referring to watching videos on the Internet, it's usually caused by a lack of bandwidth. That lack of bandwidth can be caused by your local network, your ISP or the service you're using (e.g. YouTube).